Film formation method and apparatus for forming silicon-containing insulating film doped with metal

ABSTRACT

A film formation method for a semiconductor process performs a film formation process to form a silicon-containing insulating film doped with a metal on a target substrate, in a process field inside a process container configured to be selectively supplied with a silicon source gas and a metal source gas. The method includes forming a first insulating thin layer by use of a chemical reaction of the silicon source gas, while maintaining a shut-off state of supply of the metal source gas; then, forming a first metal thin layer by use of a chemical reaction of the metal source gas, while maintaining a shut-off state of supply of the silicon source gas; and then, forming a second insulating thin layer by use of the chemical reaction of the silicon source gas, while maintaining a shut-off state of supply of the metal source gas.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a film formation method and apparatusfor a semiconductor process for forming a silicon-containing insulatingfilm doped with a metal on a target substrate, such as a semiconductorwafer. The term “semiconductor process” used herein includes variouskinds of processes which are performed to manufacture a semiconductordevice or a structure having wiring layers, electrodes, and the like tobe connected to a semiconductor device, on a target substrate, such as asemiconductor wafer or a glass substrate used for an FPD (Flat PanelDisplay), e.g., an LCD (Liquid Crystal Display), by formingsemiconductor layers, insulating layers, and conductive layers inpredetermined patterns on the target substrate.

2. Description of the Related Art

In manufacturing semiconductor devices for constituting semiconductorintegrated circuits, a target substrate, such as a semiconductor wafer,is subjected to various processes, such as film formation, etching,oxidation, diffusion, reformation, annealing, and natural oxide filmremoval. US 2006/0286817 A1 discloses a semiconductor processing methodof this kind performed in a vertical heat-processing apparatus (of theso-called batch type). According to this method, semiconductor wafersare first transferred from a wafer cassette onto a vertical wafer boatand supported thereon at intervals in the vertical direction. The wafercassette can store, e.g., 25 wafers, while the wafer boat can support 30to 150 wafers. Then, the wafer boat is loaded into a process containerfrom below, and the process container is airtightly closed. Then, apredetermined heat process is performed, while the process conditions,such as process gas flow rate, process pressure, and processtemperature, are controlled.

Nonvolatile memory devices are known as semiconductor integratedcircuits of this kind. The nonvolatile memory devices encompass floatinggate type memory devices including a floating gate and SONOS type memorydevices including an electric charge trap layer (Jpn. Pat. Appln. KOKAIPublication No. 2006-229233). Recently, SONOS type memory devicesincluding an electric charge trap layer have attracted attention,because they are relatively well operated in writing and erasing. ASONOS type memory device has a structure in which a silicon oxide film,an electric charge trap layer formed of a silicon nitride film, and asilicon oxide film are interposed between a semiconductor substrate,such as a silicon substrate, and a gate electrode made of, e.g.,poly-silicon.

The electric charge trap layer is formed of a metal-doped film, which isa silicon nitride film (SiN film) doped with a metal, such as aluminum.Where a memory device includes such a film doped with a metal, thememory device is improved in some of the operational characteristics,such as writing, erasing, and retention.

For example, as a method for forming a metal-doped film of this kind,there is a method using a CVD (Chemical Vapor Deposition) methodarranged to simultaneously supply film formation gases for forming anSiN film and a gas containing the metal into a process container.Further, there is a method for forming a film having a predeterminedthickness, by alternately and intermittently supplying film formationgases to repeatedly laminate very thin layers each having an atomic ormolecular level thickness one by one (for example, Jpn. Pat. Appln.KOKAI Publications No. 6-45256 and No. 11-087341). In general, this filmformation method is called ALD (Atomic layer Deposition) or MLD(Molecular Layer Deposition), which allows a predetermined process to beperformed without exposing wafers to a very high temperature.

Incidentally, in metal-doped films of this kind, the metal concentrationin the film and the concentration distribution in the film thicknessdirection exert large influences on some of the characteristics of themetal-doped films. However, conventional methods described above forforming a metal-doped film tend to cause the metal concentration to berelatively higher, and thus entails a difficultly in setting the metalconcentration to be relatively lower with high controllability. In thiscase, the electrical characteristic of the metal-doped film cannot besufficiently improved. Particularly, in recent years, owing to thedemands of increased miniaturization and integration of semiconductorintegrated circuits, the problem described above needs to be solved.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide a film formation methodand apparatus for a semiconductor process for forming asilicon-containing insulating film doped with a metal, which can set themetal concentration to be relatively lower with high controllability.

According to a first aspect of the present invention, there is provideda film formation method for a semiconductor process for performing afilm formation process to form a silicon-containing insulating filmdoped with a metal on a target substrate, in a process field inside aprocess container configured to be selectively supplied with a siliconsource gas and a metal source gas, the method comprising: forming afirst insulating thin layer by use of a chemical reaction of the siliconsource gas, while maintaining a shut-off state of supply of the metalsource gas; then, forming a first metal thin layer by use of a chemicalreaction of the metal source gas, while maintaining a shut-off state ofsupply of the silicon source gas; and then, forming a second insulatingthin layer by use of the chemical reaction of the silicon source gas,while maintaining a shut-off state of supply of the metal source gas, soas to laminate the first insulating thin layer, the first metal thinlayer, and the second insulating thin layer in this order.

According to a second aspect of the present invention, there is provideda computer readable medium containing program instructions for executionon a processor for performing the method according to the first aspectin a film formation apparatus for a semiconductor process including aprocess field inside a process container configured to be selectivelysupplied with a silicon source gas and a metal source gas, wherein theprogram instructions, when executed by the processor, cause the filmformation apparatus to form a silicon-containing insulating film dopedwith a metal on a target substrate inside the process field byperforming the method according to the first aspect.

According to a third aspect of the present invention, there is provideda film formation apparatus for a semiconductor process, the apparatuscomprising: a process container having a process field configured toaccommodate a target substrate; a support member configured to supportthe target substrate inside the process field; a heater configured toheat the target substrate inside the process field; an exhaust systemconfigured to exhaust gas from the process field; a supply systemconfigured to supply a silicon source gas to the process field; a supplysystem configured to supply a metal source gas to the process field; anda control section configured to control an operation of the apparatus,wherein the control section is preset to perform a film formationprocess to form a silicon-containing insulating film doped with a metalon the target substrate in the process field, the film formation processcomprising: forming a first insulating thin layer by use of a chemicalreaction of the silicon source gas, while maintaining a shut-off stateof supply of the metal source gas; then, forming a first metal thinlayer by use of a chemical reaction of the metal source gas, whilemaintaining a shut-off state of supply of the silicon source gas; andthen, forming a second insulating thin layer by use of the chemicalreaction of the silicon source gas, while maintaining a shut-off stateof supply of the metal source gas, so as to laminate the firstinsulating thin layer, the first metal thin layer, and the secondinsulating thin layer in this order.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 is a sectional view showing a film formation apparatus (verticalCVD apparatus) according to an embodiment of the present invention;

FIG. 2 is a sectional plan view showing part of the apparatus shown inFIG. 1;

FIG. 3 is a flow chart showing a film formation method according to anembodiment of the present invention;

FIG. 4 is a diagram showing the relationship between the steps of thefilm formation method and temperature according to the embodiment of thepresent invention;

FIGS. 5A and 5B are enlarged sectional views showing differentmetal-doped films respectively formed by film formation methodsaccording to the embodiment of the present invention;

FIGS. 6A and 6B are timing charts showing the gas supply and RF (radiofrequency) application used in the insulating thin layer formation stepand metal thin layer formation step, respectively of a film formationmethod according to the embodiment of the present invention;

FIGS. 7A and 7B are graphs showing the aluminum concentrationdistribution in the metal-doped films shown in FIGS. 5A and 5B,respectively, obtained by an experiment; and

FIG. 8 is a graph showing the dependency of aluminum concentration onthe temperature of the insulating thin layer formation step, obtained byan experiment.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will now be described withreference to the accompanying drawings. In the following description,the constituent elements having substantially the same function andarrangement are denoted by the same reference numerals, and a repetitivedescription will be made only when necessary.

FIG. 1 is a sectional view showing a film formation apparatus (verticalCVD apparatus) according to an embodiment of the present invention. FIG.2 is a sectional plan view showing part of the apparatus shown inFIG. 1. The film formation apparatus 2 has a process field configured tobe selectively supplied with a first process gas containing dichlorosilane (DCS) gas as a silicon source gas, a second process gascontaining ammonia (NH₃) gas as a nitriding gas or a reducing gas, and athird process gas containing TMA (trimethyl aluminum: organometalcompound) gas as a metal source gas. The film formation apparatus 2 isconfigured to form a silicon nitride film doped with aluminum (SiAlNfilm), as an example of a silicon-containing insulating film doped witha metal, on target substrates by CVD in the process field.

The apparatus 2 includes a process container 4 shaped as a cylindricalcolumn with a ceiling and an opened bottom, in which a process field 5is defined to accommodate and process a plurality of semiconductorwafers (target substrates) stacked at intervals in the verticaldirection. The entirety of the process container 4 is made of, e.g.,quartz. The top of the process container 4 is provided with a quartzceiling plate 6 to airtightly seal the top. The bottom of the processcontainer 4 is provided with a flange 8 surrounding the bottom port. Amanifold made of stainless steel may be connected to the bottom of theprocess container 4.

A wafer boat 12 made of quartz is moved up and down through the bottomport of the process container 4, so that the wafer boat 12 isloaded/unloaded into and from the process container 4. A number oftarget substrates or semiconductor wafers W are stacked on a wafer boat12. For example, in this embodiment, the wafer boat 12 has struts 12Athat can support, e.g., about 50 to 100 wafers having a diameter of 300mm at essentially regular intervals in the vertical direction.

The wafer boat 12 is placed on a table 16 through a heat-insulatingcylinder 14 made of quartz. The table 16 is supported by a rotary shaft20, which penetrates a lid 18 made of, e.g., stainless steel, and isused for opening/closing the bottom port of the process container 4.

The portion of the lid 18 where the rotary shaft 20 penetrates isprovided with, e.g., a magnetic-fluid seal 22, so that the rotary shaft20 is rotatably supported in an airtightly sealed state. A seal member24, such as an O-ring, is interposed between the periphery of the lid 18and the bottom of the process container 4, so that the interior of theprocess container 4 can be kept sealed.

The rotary shaft 20 is attached at the distal end of an arm 26 supportedby an elevating mechanism 25, such as a boat elevator. The elevatingmechanism 25 moves the wafer boat 12 and lid 18 up and down in unison.The table 16 may be fixed to the lid 18, so that wafers W are processedwithout rotation of the wafer boat 12.

A gas supply section is connected to a lower side of the processcontainer 4 to supply predetermined process gases to the process field 5within the process container 4. Specifically, the gas supply sectionincludes a second process gas supply circuit 28, a first process gassupply circuit 30, a third process gas supply circuit 32, and a purgegas supply circuit 34. The first process gas supply circuit 30 isarranged to supply a first process gas containing a silicon source gas,such as DCS (dichloro silane) gas. The second process gas supply circuit28 is arranged to supply a second process gas containing a nitriding gasor reducing gas, such as ammonia (NH₃) gas. The third process gas supplycircuit 32 is arranged to supply a third process gas containing a metalsource gas, such as TMA gas. The purge gas supply circuit 34 is arrangedto supply a purge gas comprising an inactive gas, such as N₂ gas. Eachof the first to third gases is mixed with a suitable amount of carriergas, as needed. However, such a carrier gas will not be mentioned,hereinafter, for the sake of simplicity of explanation.

More specifically, the second, first, and third process gas supplycircuits 28, 30, and 32, and the purge gas supply circuit 34 include gasdistribution nozzles 38, 40, 42 and 44, respectively, which areconnected to gas passages extending in radial directions in the flange 8of the process container 4. Each of gas distribution nozzles 38, 40, 42and 44 is formed of a quartz pipe that turns from a horizontal directionto a vertical direction and extends upward. In FIG. 1, for the sake ofsimplicity of explanation, the nozzles 38, 40, 42 and 44 are shown aspenetrating the sidewall of the process container 4 on the lower side.The gas distribution nozzles 38, 40, 42 and 44 respectively have aplurality of gas spouting holes 38A, 40A, 42A, and 44A, each set ofholes being formed at predetermined intervals in the longitudinaldirection (the vertical direction) over all the wafers W on the waferboat 12. Each set of the gas spouting holes 38A, 40A, 42A, and 44Adelivers the corresponding process gas almost uniformly in thehorizontal direction, so as to form gas flows parallel with the wafers Won the wafer boat 12.

The nozzles 38, 40, 42, and 44 are connected to gas sources 28S, 30S,32S, and 34S of NH₃ gas, DCS gas, TMA gas, and N₂ gas, respectively,through gas supply lines (gas passages) 48, 50, 52, and 54,respectively. The gas supply lines 48, 50, 52, and 54 are provided withswitching valves 48A, 50A, 52A, and 54A and flow rate controllers 48B,50B, 52B, and 54B, such as mass flow controllers, respectively. Withthis arrangement, NH₃ gas, DCS gas, TMA gas, and N₂ gas can be suppliedat controlled flow rates.

A gas exciting section 66 is formed at the sidewall of the processcontainer 4 in the vertical direction. On the side of the processcontainer 4 opposite to the gas exciting section 66, a long narrowexhaust port 68 for vacuum-exhausting the inner atmosphere is formed bycutting the sidewall of the process container 4 in, e.g., the verticaldirection.

Specifically, the gas exciting section 66 has a vertically long narrowopening 70 formed by cutting a predetermined width of the sidewall ofthe process container 4 in the vertical direction. The opening 70 iscovered with a quartz cover 72 airtightly connected to the outer surfaceof the process container 4 by welding. The cover 72 has a vertical longnarrow shape with a concave cross-section, so that it projects outwardfrom the process container 4.

With this arrangement, the gas exciting section 66 is formed such thatit projects outward from the sidewall of the process container 4 and isopened on the other side to the interior of the process container 4. Inother words, the inner space of the gas exciting section 66 communicateswith the process field 5 within the process container 4. The opening 70has a vertical length sufficient to cover all the wafers W on the waferboat 12 in the vertical direction.

A pair of long narrow electrodes 74 are disposed on the opposite outersurfaces of the cover 72, and face each other in the longitudinaldirection (the vertical direction). The electrodes 74 are connected toan RF (Radio Frequency) power supply 76 for plasma generation, throughfeed lines 78. An RF voltage of, e.g., 13.56 MHz is applied to theelectrodes 74 to form an RF electric field for exciting plasma betweenthe electrodes 74. The frequency of the RF voltage is not limited to13.56 MHz, and it may be set at another frequency, e.g., 400 kHz.

The gas distribution nozzle 38 of the second process gas is bent outwardin the radial direction of the process container 4, at a position lowerthan the lowermost wafer W on the wafer boat 12. Then, the gasdistribution nozzle 38 vertically extends at the deepest position (thefarthest position from the center of the process container 4) in the gasexciting section 66. As shown also in FIG. 2, the gas distributionnozzle 38 is separated outward from an area sandwiched between the pairof electrodes 74 (a position where the RF electric field is mostintense), i.e., a plasma generation area PS where the main plasma isactually generated. The second process gas containing NH₃ gas is spoutedfrom the gas spouting holes 38A of the gas distribution nozzle 38 towardthe plasma generation area PS. Then, the second process gas is excited(decomposed or activated) in the plasma generation area PS, and issupplied in this state onto the wafers W on the wafer boat 12.

An insulating protection cover 80 made of, e.g., quartz is attached onand covers the outer surface of the cover 72. A cooling mechanism (notshown) is disposed in the insulating protection cover 80 and comprisescoolant passages respectively facing the electrodes 74. The coolantpassages are supplied with a coolant, such as cooled nitrogen gas, tocool the electrodes 74. The insulating protection cover 80 is coveredwith a shield (not shown) disposed on the outer surface to prevent RFleakage.

At positions near and outside the opening 70 of the gas exciting section66, the gas distribution nozzles 40, 42, and 44 of the first and thirdprocess gases and the purge gas are disposed. Specifically, the gasdistribution nozzles 40 and 42 extend upward on one side of the outsideof the opening 70 (in the process container 4), and the gas distributionnozzle 44 extends upward on the other side. The first process gascontaining DCS gas, the third process gas containing TMA gas, and thepurge gas comprising N₂ gas are spouted from the gas spouting holes 40A,42A, and 44A of the gas distribution nozzles 40, 42, and 44,respectively, toward the center of the process container 4.

On the other hand, the exhaust port 68, which is formed opposite the gasexciting section 66, is covered with an exhaust port cover member 82.The exhaust port cover member 82 is made of quartz with a U-shapecross-section, and attached by welding. The exhaust cover member 82extends downward along the sidewall of the process container 4 and thenturns into a horizontal state to provide a gas outlet 84. The gas outlet84 is connected to a vacuum-exhaust system GE including a pressureregulation valve 86 and a vacuum pump 88.

The process container 4 is surrounded by a heater 90, which is used forheating the atmosphere within the process container 4 and the wafers W.A thermocouple (not shown) is disposed near the exhaust port 68 in theprocess container 4 to control the heater 90.

The film formation apparatus 2 further includes a main control section92 formed of, e.g., a computer, to control the entire apparatus. Themain control section 92 can control the film formation process describedbelow in accordance with the process recipe of the film formationprocess concerning, e.g., the film thickness and composition of a filmto be formed, stored in the storage portion 94 thereof in advance. Inthe storage portion 94, the relationship between process conditions,such as process gas flow rates, and the thickness and composition of thefilm is also stored as control data in advance. Accordingly, the maincontrol section 92 can control the elevating mechanism 25, gas supplycircuits 28, 30, 32, 34, and 34, exhaust system GE, gas exciting section66, heater 90, and so forth, based on the stored process recipe andcontrol data.

Next, an explanation will be given of a film formation method performedin the apparatus shown in FIG. 1. In this film formation method, asilicon nitride film doped with aluminum (SiAlN film), as an example ofa silicon-containing insulating film doped with a metal, is formed onsemiconductor wafers. In order to achieve this, a first process gascontaining dichloro silane (DCS) gas as a silicon source gas, a secondprocess gas containing ammonia (NH₃) gas as a nitriding gas or reducinggas, and a third process gas containing TMA gas as a metal source gasare selectively supplied into the process field 5 accommodating wafersW. Specifically, a film formation process is performed along with thefollowing operations.

At first, the wafer boat 12 at room temperature, which supports a numberof, e.g., 50 to 100, wafers having a diameter of 300 mm, is loaded intothe process container 4 heated at a predetermined temperature, and theprocess container 4 is airtightly closed. Then, the interior of theprocess container 4 is vacuum-exhausted and kept at a predeterminedprocess pressure, and the wafer temperature is increased to a processtemperature for film formation. At this time, the apparatus is in awaiting state until the temperature becomes stable. Then, while thewafer boat 12 is rotated, the first to third process gases and the purgegas are supplied from the respective gas distribution nozzles 40, 38,42, and 44 at controlled flow rates with timings described later. Duringthe film formation process, the interior of the process container 4 iskept vacuum-exhausted.

FIG. 3 is a flow chart showing a film formation method according to anembodiment of the present invention. As shown in FIG. 3, this embodimentis arranged to alternately repeat, a plurality of times, a step offorming an insulating thin layer by use of the silicon source gas and astep of forming a metal thin layer by use of the metal source gas, so asto form a silicon-containing insulating film doped with a metal.

In the insulating thin layer formation step, the first process gascontaining DCS gas and the second process gas containing NH₃ gas areused. In the metal thin layer formation step, the third process gascontaining TMA gas and the second process gas containing NH₃ gas areused. Between the insulating thin layer formation step and metal thinlayer formation step, there is interposed an inter-layer purge step(intermediate step) of supplying the purge gas into the processcontainer 4 to remove the residual gas. The film formation processstarts with the insulating thin layer formation step and ends with theinsulating thin layer formation step.

FIG. 3 shows a case where the insulating thin layer formation step andthe metal thin layer formation step with the inter-layer purge stepinterposed therebetween are repeated in accordance with Step S1 to StepSn (“n” is a positive integer of 3 or more). In this case, since “n” is3 or more, at least one metal thin layer is formed.

FIG. 4 is a diagram showing the relationship between the steps of thefilm formation method and temperature according to the embodiment of thepresent invention. As shown in FIG. 4, the process temperature of themetal thin layer formation step is preferably adjusted to an optimumvalue from that of the insulating thin layer formation step inaccordance with the type of the metal source gas used in the metal thinlayer formation step. This adjustment with a temperature increase ordecrease is performed within the inter-layer purge step.

For example, the length of the inter-layer purge step is about 0.5 to2.0 hours, although it depends on the volume of the process container 4.In FIG. 3, the lengths of insulating thin layer formation steps S1, S3 .. . and the lengths of metal thin layer formation steps S2, S4 . . . maybe respectively adjusted. Where the lengths of the respective steps aresuitably adjusted, the metal-doped film can be controlled in terms ofthe metal concentration therein and the metal concentration distributionin the film thickness direction.

FIGS. 5A and 5B are enlarged sectional views showing differentmetal-doped films respectively formed by film formation methodsaccording to the embodiment of the present invention. FIG. 5A shows acase where “in”=3 in FIG. 3, and FIG. 5B shows a case where “n”=7 inFIG. 3. Specifically, in the case shown in FIG. 5A, a metal-doped film100 formed on the surface of a semiconductor wafer W consists of a firstinsulating thin layer 102 made of SiN formed in Step S1 of FIG. 3, afirst metal thin layer 104 made of Al formed in Step S2, and a secondinsulating thin layer 106 made of SiN formed in Step S3 laminated inthis order.

In the metal-doped film 100 shown in FIG. 5A, the first metal thin layer104 has a very small thickness, and the insulating thin layers 102 and106 above and below the layer 104 have large thicknesses. In this case,the metal-doped film 100 is designed such that the metal concentrationis highest at the center in the film thickness direction. FIG. 5Aclearly shows the border lines between the layers of the metal-dopedfilm 100, but the border lines are not so clear in fact. This is so,because the metal, i.e., aluminum in the metal thin layer 104 isthermally diffused into the insulating thin layers 102 and 106 on itsupper and lower sides due to the temperature of the film formation stepsand a heating process performed as a post step.

In the case shown in FIG. 5B, a metal-doped film 110 consists of a firstinsulating thin layer 112 made of SiN formed in Step S1 of FIG. 3, afirst metal thin layer 114 made of Al formed in Step S2, a secondinsulating thin layer 116 made of SiN formed in Step S3, a second metalthin layer 118 made of Al formed in Step S4, a third insulating thinlayer 120 made of SiN formed in Step S5, a third metal thin layer 122made of Al formed in Step S6, and a fourth insulating thin layer 124made of SiN formed in Step S7 laminated in this order. In this case,unlike the case shown in FIG. 5A, the metal-doped film 110 is designedsuch that the metal concentration is almost constant in the filmthickness direction.

FIG. 5B also clearly shows the border lines between the layers of themetal-doped film 110, but the border lines are not so clear in fact.This is so, because the metal, i.e., aluminum in the metal thin layers114, 118, and 122 is thermally diffused into the insulating thin layers112, 116, 120, and 124 on their upper and lower sides due to thetemperature of the film formation steps and a heating process performedas a post step.

FIGS. 5A and 5B merely show examples of a metal-doped film, and thenumber of insulating thin layers and metal thin layers laminated one ontop of the other is not limited to these examples. FIGS. 5A and 5B showstructures in each of which a metal-doped film is directly formed on awafer W for the sake of simplicity of explanation, but another thin filmmay be interposed between the wafer W and metal-doped film.

FIG. 6A is a timing chart showing the gas supply and RF (radiofrequency) application used in the insulating thin layer formation stepof a film formation method according to the embodiment of the presentinvention. As shown in FIG. 6A, in the insulating thin layer formationstep, the first process gas containing DCS gas as a silicon source gasand the second process gas containing NH₃ gas as a nitriding gas areused, and the first to fourth sub-steps T1 to T4 are alternatelyrepeated. A cycle comprising the first to fourth sub-steps T1 to T4 isperformed once or repeated a plurality of times, and very thin layers ofsilicon nitride formed by respective cycles are laminated, therebyarriving at an insulating thin layer having a target thickness.

Specifically, the first sub-step T1 is arranged to perform supply of thefirst process gas (denoted as DCS in FIG. 6A) to the process field 5,while maintaining the shut-off state of supply of the second process gas(denoted as NH₃ in FIG. 6A) to the process field 5. The second sub-stepT2 is arranged to maintain the shut-off state of supply of the first andsecond process gases to the process field 5. The third sub-step T3 isarranged to perform supply of the second process gas to the processfield 5, while maintaining the shut-off state of supply of the firstprocess gas to the process field 5. The fourth sub-step T4 is arrangedto maintain the shut-off state of supply of the first and second processgases to the process field 5.

Each of the second and fourth sub-steps T2 and T4 is used as a purgesub-step to remove the residual gas within the process container 4. Theterm “purge” means removal of the residual gas within the processcontainer 4 by vacuum-exhausting the interior of the process container 4while supplying an inactive gas, such as N₂ gas, into the processcontainer 4, or by vacuum-exhausting the interior of the processcontainer 4 while maintaining the shut-off state of supply of all thegases. In this respect, the second and fourth sub-steps T2 and T4 may bearranged such that the first half utilizes only vacuum-exhaust and thesecond half utilizes both vacuum-exhaust and inactive gas supply.

In the third sub-step T3, the RF power supply 76 is set in the ON-stateto turn the second process gas into plasma by the gas exciting section66, so as to supply the second process gas in an activated state to theprocess field 5. Consequently, radicals derived from NH₃ gas aregenerated and enhance the reactivity with molecules of DCS gas and soforth adsorbed on the surface of the wafers W.

More specifically, the first process gas containing DCS gas is suppliedfrom the gas spouting holes 40A of the gas distribution nozzle 40 toform gas flows parallel with the wafers W on the wafer boat 12. Whilebeing supplied, molecules of the DCS gas and molecules and atoms ofdecomposition products generated by decomposition are adsorbed on thewafers W.

On the other hand, the second process gas containing NH₃ gas is suppliedfrom the gas spouting holes 38A of the gas distribution nozzle 38 toform gas flows parallel with the wafers W on the wafer boat 12. Thesecond process gas is excited and partly turned into plasma when itpasses through the plasma generation area PS between the pair ofelectrodes 74. At this time, for example, radicals (activated species),such as N*, NH*, NH₂*, and NH₃*, are produced (the symbol ┌*┘ denotesthat it is a radical). The radicals and so forth derived from the NH₃gas flow out from the opening 70 of the gas exciting section 66 towardthe center of the process container 4, and are supplied into gapsbetween the wafers W in a laminar flow state.

The radicals and so forth react with (nitride) molecules and so forth ofDCS gas adsorbed on the surface of the wafers W, so that a very thinlayer of silicon nitride of an atomic level or molecular level is formedon the wafers W. Alternatively, when the DCS gas flows onto radicals andso forth derived from the NH₃ gas adsorbed on the surface of the wafersW, the same reaction is caused, so a silicon nitride layer is formed onthe wafers W. The very thin layer of silicon nitride formed by one cyclecomprising the first to fourth sub-steps T1 to T4 is set to have athickness of about 0.1 nm. The cycle is repeated to laminate very thinlayers of silicon nitride until an insulating thin layer having apredetermined thickness is formed.

The insulating thin layers 102, 106, 112, 116, 120, and 124 shown inFIGS. 5A and 5B are formed by the film formation process describedabove. The sub-step T1 of supplying the first process gas containing DCSgas is set to be about 3 to 60 seconds. The sub-step T3 of supplying thesecond process gas containing NH₃ gas is set to be about 10 to 120seconds. Each of the purge sub-steps T2 and T4 is set to be about 10 to60 seconds.

FIG. 6B is a timing chart showing the gas supply and RF (radiofrequency) application used in the metal thin layer formation step of afilm formation method according to the embodiment of the presentinvention. As shown in FIG. 6B, in the metal thin layer formation step,the third process gas containing TMA gas as a metal source gas and thesecond process gas containing NH₃ gas as a reactive gas are used, andthe first to fourth sub-steps T11 to T14 are alternately repeated. Acycle comprising the first to fourth sub-steps T11 to T14 is performedonce or repeated a plurality of times, and very thin layers of the metalformed by respective cycles are laminated, thereby arriving at a metalthin layer having a target thickness.

Specifically, the first sub-step T11 is arranged to perform supply ofthe third process gas (denoted as TMA in FIG. 6B) to the process field5, while maintaining the shut-off state of supply of the second processgas (denoted as NH₃ in FIG. 6B) to the process field 5. The secondsub-step T12 is arranged to maintain the shut-off state of supply of thesecond and third process gases to the process field 5. The thirdsub-step T13 is arranged to perform supply of the second process gas tothe process field 5, while maintaining the shut-off state of supply ofthe third process gas to the process field 5. The fourth sub-step T14 isarranged to maintain the shut-off state of supply of the second andthird process gases to the process field 5. Each of the second andfourth sub-steps T12 and T14 is used as a purge sub-step to remove theresidual gas within the process container 4.

In the third sub-step T13, the RF power supply 76 is set in the ON-stateto turn the second process gas into plasma by the gas exciting section66, so as to supply the second process gas in an activated state to theprocess field 5. Consequently, radicals derived from NH₃ gas aregenerated, and enhance the reactivity with molecules of TMA gas and soforth adsorbed on the surface of the wafers W.

More specifically, the third process gas containing TMA gas is suppliedfrom the gas spouting holes 42A of the gas distribution nozzle 42 toform gas flows parallel with the wafers W on the wafer boat 12. Whilebeing supplied, molecules of the TMA gas and molecules and atoms ofdecomposition products generated by decomposition are adsorbed on thewafers W.

On the other hand, the second process gas containing NH₃ gas is suppliedfrom the gas spouting holes 38A of the gas distribution nozzle 38 toform gas flows parallel with the wafers W on the wafer boat 12. Thesecond process gas is excited and partly turned into plasma when itpasses through the plasma generation area PS between the pair ofelectrodes 74. The radicals and so forth derived from the NH₃ gas flowout from the opening 70 of the gas exciting section 66 toward the centerof the process container 4, and are supplied into gaps between thewafers W in a laminar flow state.

The radicals and so forth react with molecules and so forth of TMA gasadsorbed on the surface of the wafers W, so that a very thin layer ofthe metal of an atomic level or molecular level is formed on the wafersW. The very thin layer of the metal formed by one cycle comprising thefirst to fourth sub-steps T11 to T14 is set to have a thickness of about0.1 nm. The cycle is repeated to laminate very thin layers of the metaluntil a metal thin layer having a predetermined thickness is formed.

The metal thin layers 104, 114, 118, and 122 shown in FIGS. 5A and 5Bare formed by the film formation process described above. The sub-stepT11 of supplying the third process gas containing TMA gas is set to beabout 3 to 60 seconds. The sub-step T13 of supplying the second processgas containing NH₃ gas is set to be about 10 to 120 seconds. Each of thepurge sub-steps T12 and T14 is set to be about 10 to 60 seconds.

In the timing charts shown in FIGS. 6A and 6B, the film formationprocess can be started with and end with any sub-step of supplying thefirst process gas containing DCS gas, the third process gas containingTMA gas, the second process gas containing NH₃ gas, or purge gas.

In the insulating thin layer formation step, the process pressure is setto be within a range of 70 to 860 Pa, and the process temperature is setto be within a range of 400 to 600° C., and preferably of 450 to 550° C.(see FIG. 4). In the metal thin layer formation step, the processpressure is set to be within a range of 4 to 200 Pa, and the processtemperature is set to be within a range of 150 to 300° C., andpreferably of 200 to 250° C.

In FIG. 5A, the first insulating thin layer 102 is set to have athickness of about 2.0 to 10.0 nm, such as about 3.9 nm, the first metalthin layer 104 is set to have a thickness of about 0.1 to 1.0 nm, suchas about 0.1 to 0.3 nm, and the second insulating thin layer 106 is setto have a thickness of about 2.0 to 10.0 nm, such as about 4.0 nm. InFIG. 5B, each of the first and fourth insulating thin layers 112 and 124is set to have a thickness of about 0.1 to 1.5 nm, such as about 0.2 to0.5 nm, each of the second and third insulating thin layers 116 and 120is set to have a thickness of about 0.2 to 3.0 nm, such as about 0.4 to1.0 nm, and each of the first, second, and third metal thin layers 114,118, and 122 is set to have a thickness of about 0.1 to 0.6 nm, such asabout 0.1 to 0.3 nm.

In the film formation method according to this embodiment, where ametal-doped film 100 or 110 is formed, an insulating thin layerformation step of forming an insulating thin layer by use of a siliconsource gas and a metal thin layer formation step of forming a metal thinlayer by use of a metal source gas containing a metal, such as aluminum,are alternately repeated such that the metal thin layer formation stepis included at least once. Consequently, it is possible to form asilicon-containing insulating film doped with a metal while setting themetal concentration to be relatively lower with high controllability andadjusting the metal concentration distribution in the film thicknessdirection.

Particularly, where the total thickness of metal thin layers is set tobe far smaller than the total thickness of insulating thin layers, themetal concentration in the metal-doped film becomes very low. Such ametal-doped film is effectively applicable to the electric charge traplayer of a memory device, as described above.

<Experiment 1>

A metal-doped film 100 shown in FIG. 5A and a metal-doped film 110 shownin FIG. 5B were respectively formed by film formation methods accordingto the embodiment described above, and the metal concentration of thefilms were measured. DCS gas was used as a silicon source gas, TMA gaswas used as a metal source gas, and NH₃ gas was used as a nitriding gasor reactive gas. Al in the metal-doped film was measured by SIMS(secondary ion mass spectrometry).

The metal-doped film 100 shown in FIG. 5A was formed such that the cycleshown in FIG. 6A was repeated 40 times to form each of the first andsecond insulating thin layers 102 and 106, and the cycle shown in FIG.6B was repeated 6 times to form the first metal thin layer 104. Themetal-doped film 110 shown in FIG. 5B was formed such that the cycleshown in FIG. 6A was repeated 3 times to form each of the first andfourth insulating thin layers 112 and 124, the cycle shown in FIG. 6Awas repeated 6 times to form each of the second and third insulatingthin layers 116 and 120, and the cycle shown in FIG. 6B was performedonce to form each of the first, second, and third metal thin layers 114,118, and 120.

FIGS. 7A and 7B are graphs showing the aluminum concentrationdistribution in the metal-doped films shown in FIGS. 5A and 5B,respectively, obtained by the experiment. As shown in FIG. 7A, where themetal-doped film was formed to include only one metal thin layer, the Alconcentration had an acute peak near the center in the film thicknessdirection. On the other hand, as shown in FIG. 7B, where the metal-dopedfilm was formed to have separate three metal thin layers, the Alconcentration was almost uniformly diffused or distributed in the filmthickness direction.

Accordingly, the metal concentration can be adjusted in the thicknessdirection of the metal-doped film by presetting the number of metal thinlayers to be formed. Further, the level of the metal concentration canbe controlled by presetting the thickness of each metal thin layer.

<Experiment 2>

The controllability of the metal concentration in the metal-doped filmwas examined by use of film formation methods according to theembodiment described above. In film formation apparatuses practicallyused, it is difficult to stably supply a small amount of metal sourcegas, and so it is not easy to address a metal doping amount for a lowerconcentration. In light of this, a method according to the embodimentdescribed above may be arranged to sublimate or evaporate part of ametal thin layer previously formed, so as to practically realize a metaldoping amount for a lower concentration. For example, after a metal thinlayer is formed by the metal thin layer formation step (such as Step S4in FIG. 4), the process temperature of the subsequent insulating thinlayer formation step (S5) is controlled, so that the thickness of themetal thin layer is adjusted.

In this experiment, a metal-doped film 100 shown in FIG. 5A was formedwhile the process temperature t1 of the insulating thin layer formationstep for forming the second insulating thin layer 106 was set atdifferent values of 450° C. and 550° C. The process temperature of themetal thin layer formation step was set at 250° C., and the length TP ofthe inter-layer purge step (see FIG. 4) was set at one hour.

FIG. 8 is a graph showing the dependency of aluminum concentration onthe temperature of the insulating thin layer formation step, obtained byan experiment. In FIG. 8, the Al metal concentration is shown asconverted to a value obtained by setting the total thickness of themetal-doped film at 7.0 nm. As shown in FIG. 8, the theoretical value ofthe metal concentration corresponding to the thickness of a metal thinlayer formed by the metal thin layer formation step was 0.859 [atom %].On the other hand, where the process temperature t1 of the insulatingthin layer formation step performed immediately thereafter was set at450° C., the metal concentration was decreased to 0.323 [atom %].Further, where the process temperature t1 was set at 550° C., the metalconcentration was further decreased to 0.139 [atom %].

Accordingly, after a metal thin layer is formed by the metal thin layerformation step, the insulating thin layer formation step performedimmediately thereafter is set to use a process temperature adjustedwithin a permissible range (the process temperature is used as aparameter). In this case, the metal thin layer is sublimated orevaporated by a predetermined amount to have a modified thickness, sothat the metal concentration can be controlled within a far lowerconcentration range.

From the same point of view, the length TP or set temperature of aninter-layer purge step may be alternatively used as a parameter for thispurpose. In this case, the metal thin layer formed immediately beforethe inter-layer purge step is sublimated or evaporated by apredetermined amount to have a modified thickness, so that the metalconcentration can be controlled within a far lower concentration range.

<Modification>

In the embodiment described above, as shown in FIGS. 6A and 6B, each ofthe insulating thin layer formation step and metal thin layer formationstep are arranged such that RF is turned on to generate plasma andthereby to activate NH₃ gas in the sub-step of supplying the secondprocess gas containing NH₃ gas as a nitriding gas or reactive gas.However, the insulating thin layer formation step and/or metal thinlayer formation step may be arranged not to use plasma for activatingNH₃ gas in supplying the NH₃ gas.

As shown in FIG. 6B, the metal thin layer formation step includes asub-step of supplying the second process gas containing the reactive gas(NH₃). However, the metal thin layer formation step may merely supplythe third process gas containing TMA gas without supplying the secondprocess gas containing the reactive gas (NH₃) (and thus, plasma is notgenerated). In this case, if an organometal compound including anorganic functional group or amide group is used as a metal source gas, acarbon component or hydrogen component may be mixed into the metal thinlayer and adversely affect some of the characteristics thereof. However,in the insulating thin layer formation step performed immediately afterthe metal thin layer formation step, plasma is generated (see FIG. 6A)and serves to remove the carbon component or hydrogen component from themetal thin layer, and so the characteristics thereof can be hardlyadversely affected.

In the embodiment described above, as shown in FIGS. 6A and 6B, each ofthe insulating thin layer formation step and metal thin layer formationstep are arranged such that two process gases are alternately suppliedin accordance with an ALD or MLD method. Alternatively, the insulatingthin layer formation step and/or metal thin layer formation step may bearranged such that two process gases are simultaneously supplied inaccordance with an ordinary CVD method. In such a modification, plasmafor activating NH₃ gas may be not used in supplying the NH₃ gas inaccordance with an ordinary thermal CVD method.

In the embodiment described above, a silicon nitride film (SiN) isformed as the insulating thin layer, but a silicon oxide film (SiO₂) maybe formed for the same purpose by supplying an oxidizing gas in place ofthe nitriding gas.

In the embodiment described above, the silicon source gas contained inthe first process gas is exemplified by DCS gas. In this respect, thesilicon source gas may comprise one or more gases selected from thegroup consisting of DCS (dichloro silane), tetraethoxy silane (TEOS),tetramethyl silane (TMS), HCD (hexachloro disilane), monosilane (SiH₄),disilane (Si₂H₆), HMDS (hexamethyl disilazane), TCS (trichloro silane),DSA (disilylamine), TSA (trisilylamine), BTBAS (bistertialbutylaminosilane), 3DMAS (trisdimethylamino silane), 4DMAS (tetrakisdimethylaminosilane), TEMASiH (trisethylmethylamino silane), TEMASi(tetrakis-ethylmethylamino silane), and Si(MMP)₄(tetrakis-methoxymethylpropoxy silane).

In the embodiment described above, the metal source gas contained in thethird process gas is exemplified by TMA gas. In this respect, the metalsource gas may comprise one or more gases selected from the groupconsisting of TMA (trimethyl aluminum), Cu(hfac)TMVS(hexafluoroacetylacetonate-trimethyl-vinylsilyl copper), Cu(EDMDD)₂,TBTDET (tertiary-butylimide-tridiethylamide tantalum), PET (pentaethoxytantalum), TiCl₄ (titanium tetrachloride), AlCl₃ (aluminum trichloride),TEH (tetrakisethoxy hafnium), Zr(OtBt)₄, HTTB (hafniumtetratertiarybutoxide), TDMAH (tetrakisdimethylamino hafnium), TDEAH(tetrakis-diethylamino hafnium), TEMAH (tetrakisethylmethylaminohafnium), Hf(MMP)₄ (tetrakismethoxymethylpropoxy hafnium), ZTTB(zirconiumtetratertiarybutoxide), TDMAZ (tetrakisdimethylaminozirconium), TDEAZ (tetrakis-diethylamino zirconium), TEMAZ(tetrakis-ethylmethylamino zirconium), Zr(MMP)₄(tetrakis-methoxymethylpropoxy zirconium), TEA (tetraethyl aluminum),and Al(MMP)₃ (trismethoxymethylpropoxy aluminum).

A nitriding gas for forming a silicon nitride film may comprise NH₃ orN₂ gas. An oxidizing gas for forming a silicon oxide film may compriseone or more gases selected from the group consisting of O₂, O₃, H₂O,H₂O₂, N₂O, and NO. A purge gas may comprise an inactive gas, such as N₂gas or a rare gas, e.g., He or Ar.

In the embodiment described above, the film formation apparatus isexemplified by a film formation apparatus of the batch type thatprocesses a plurality of target substrates all together. Alternatively,the present invention may be applied to a single-substrate filmformation apparatus that processes target substrates one by one. Atarget substrate is not limited to a semiconductor wafer, and it may beanother substrate, such as an LCD substrate or glass substrate.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A film formation method for a semiconductor process for performing afilm formation process to form a silicon-containing insulating filmdoped with a metal on a target substrate, in a process field, inside aprocess container configured to be selectively supplied with a siliconsource gas and a metal source gas, the method comprising: forming afirst insulating thin layer by use of a chemical reaction of the siliconsource gas, while maintaining a shut-off state of supply of the metalsource gas; then, forming a first metal thin layer by use of a chemicalreaction of the metal source gas, while maintaining a shut-off state ofsupply of the silicon source gas; and then, forming a second insulatingthin layer by use of the chemical reaction of the silicon source gas,while maintaining a shut-off state of supply of the metal source gas, soas to laminate the first insulating thin layer, the first metal thinlayer, and the second insulating thin layer in this order, wherein theprocess field is configured to be selectively supplied with a NH₃ gas,each of said forming a first insulating thin layer and said forming asecond insulating thin layer is arranged to cause the NH₃ gas tochemically react with the silicon source gas, and said forming a firstmetal thin layer is arranged to cause the NH₃ gas to chemically reactwith the metal source gas.
 2. The method according to claim 1, whereinthe first metal thin layer has a thickness of 0.1 to 1.0 nm.
 3. Themethod according to claim 1, wherein the silicon-containing insulatingfilm doped with a metal comprises the first insulating thin layer as alowermost layer.
 4. The method according to claim 1, wherein thesilicon-containing insulating film doped with a metal comprises thesecond insulating thin layer as an uppermost layer.
 5. The methodaccording to claim 1, wherein, subsequently to said forming a secondinsulating thin layer, the method further comprises: forming a secondmetal thin layer by use of the chemical reaction of the metal sourcegas, while maintaining a shut-off state of supply of the silicon sourcegas; and then, forming a third insulating thin layer by use of thechemical reaction of the silicon source gas, while maintaining ashut-off state of supply of the metal source gas, so as to laminate thefirst insulating thin layer, the first metal thin layer, the secondinsulating thin layer, the second metal thin layer, and the thirdinsulating thin layer in this order.
 6. The method according to claim 5,wherein each of the first and second metal thin layers has a thicknessof 0.1 to 0.6 nm, and the second insulating thin layer has a thicknessof 0.2 to 3.0 nm.
 7. The method according to claim 1, wherein saidforming a first metal thin layer is arranged to alternately repeat, aplurality of times, a first supply sub-step of performing supply of themetal source gas to the process field, while maintaining a shut-offstate of supply of the NH₃ gas, and a second supply sub-step ofperforming supply of the NH₃ gas to the process field, while maintaininga shut-off state of supply of the metal source gas.
 8. The methodaccording to claim 7, wherein the second supply sub-step comprises anexcitation period of supplying the NH₃ gas to the process field whileexciting the NH₃ gas by a plasma exciting mechanism.
 9. The methodaccording to claim 1, wherein the method further comprises first andsecond intermediate steps of exhausting residual gas from the processfield while maintaining a shut-off state of supply of the silicon sourcegas and the metal source gas, respectively, between said forming a firstinsulating thin layer and said forming a first metal thin layer andbetween said forming a first metal insulating thin layer and saidforming a second insulating thin layer.
 10. The method according toclaim 9, wherein the method further comprises using a set temperature ofthe second intermediate step as a parameter to modify a thickness of thefirst metal thin layer, thereby controlling a metal concentration in thesilicon-containing insulating film doped with a metal.
 11. The methodaccording to claim 9, wherein the method further comprises using alength of the second intermediate step as a parameter to modify athickness of the first metal thin layer, thereby controlling a metalconcentration in the silicon-containing insulating film doped with ametal.
 12. The method according to claim 1, wherein each of said forminga first insulating thin layer and said forming a second insulating thinlayer is arranged to alternately repeat, a plurality of times, a firstsupply sub-step of performing supply of the silicon source gas to theprocess field, while maintaining a shut-off state of supply of the NH₃gas, and a second supply sub-step of performing supply of the NH₃ gas tothe process field, while maintaining a shut-off state of supply of thesilicon source gas.
 13. The method according to claim 12, wherein thesecond supply sub-step comprises an excitation period of supplying theNH₃ gas to the process field while exciting the NH₃ gas by a plasmaexciting mechanism.
 14. The method according to claim 1, wherein thesilicon source gas comprises at least one gas selected from the groupconsisting of DCS (dichloro silane), tetraethoxy silane (TEOS),tetramethyl silane (TMS), HCD (hexachloro disilane), monosilane (SiH₄),disilane (Si₂H₆), HMDS (hexamethyl disilazane), TCS (trichloro silane),DSA (disilylamine), TSA (trisilylamine), BTBAS (bistertialbutylaminosilane), 3DMAS (trisdimethylamino silane), 4DMAS (tetrakisdimethylaminosilane), TEMASiH (trisethylmethylamino silane), TEMASi(tetrakis-ethylmethylamino silane), and Si(MMP)₄(tetrakis-methoxymethylpropoxy silane).
 15. The method according toclaim 1, wherein the metal source gas comprises at least one gasselected from the group consisting of TMA (trimethyl aluminum),Cu(hfac)TMVS (hexafluoroacetylacetonate-trimethyl-vinylsilyl copper),Cu(EDMDD)₂, TBTDET (tertiary-butylimide-tridiethylamide tantalum), PET(pentaethoxy tantalum), TiCl₄ (titanium tetrachloride), AlCl₃ (aluminumtrichloride), TEH (tetrakisethoxy hafnium), Zr(OtBt)₄, HTTB (hafniumtetratertiarybutoxide), TDMAH (tetrakisdimethylamino hafnium), TDEAH(tetrakis-diethylamino hafnium), TEMAH (tetrakisethylmethylaminohafnium), Hf(MMP)₄ (tetrakismethoxymethylpropoxy hafnium), ZTTB(zirconiumtetratertiarybutoxide), TDMAZ (tetrakisdimethylaminozirconium), TDEAZ (tetrakis-diethylamino zirconium), TEMAZ(tetrakis-ethylmethylamino zirconium), Zr(MMP)₄(tetrakis-methoxymethylpropoxy zirconium), TEA (tetraethyl aluminum),and Al(MMP)₃ (trismethoxymethylpropoxy aluminum).
 16. A computerreadable non-transitory storage medium containing program instructionsfor execution on a processor for performing the method according toclaim 1 in a film formation apparatus for a semiconductor processincluding the process field inside the process container, wherein theprogram instructions, when executed by the processor, cause the filmformation apparatus to form a silicon-containing insulating film dopedwith a metal on a target substrate inside the process field byperforming the method according to claim
 1. 17. A film formationapparatus for a semiconductor process, the apparatus comprising: aprocess container having a process field configured to accommodate atarget substrate; a support member configured to support the targetsubstrate inside the process field; a heater configured to heat thetarget substrate inside the process field; an exhaust system configuredto exhaust gas from the process field; a supply system configured tosupply a silicon source gas to the process field; a supply systemconfigured to supply a metal source gas to the process field; a supplysystem configured to supply a NH₃ gas to the process field; and acontrol section configured to control an operation of the apparatus, andincluding a computer readable non-transitory storage medium containingprogram instructions for execution on a processor, wherein the programinstructions, when executed by the processor, cause the film formationapparatus to form a silicon-containing insulating film doped with ametal on the target substrate inside the process field by performing themethod according to claim 1.